U.S. Pat. No. 4,183,834 discloses tackifiers for various elastomeric latices made from a rosin acid, e.g., modified tall oil rosin or rosin acid oligomer, instead of the modified olefinic hydrocarbon resins of the present invention. It has been found that while the tackifier compositions of the aforesaid patent are particularly suited to tackifying synthetic elastomeric latices such as SBR (carboxylated butadiene/styrene) they are not as well suited to the tackifying of natural rubber latices. Surprisingly, the tackifiers of the present invention are especially well suited to the tackifying of natural rubber latices.
The tackifiers of the present invention are not of themselves novel. However, the combination of an emulsified tackifier composition with a latex, is believed novel especially where the latex consists of or comprises natural rubber latex. Of particular utility as tackifiers for natural rubber containing latices are the terpene hydrocarbon type tackifiers hereinafter more particularly described.
The prior art has described numerous unsaturated hydrocarbon polymers which polymers are then modified with an alpha-beta unsaturated carboxylic acid, such as maleic anhydride, optionally esterified, neutralized and dispersed in water. Such materials are to be distinguished from copolymers of maleic anhydride, for example, and a monomeric terpene hydrocarbon such as disclosed by Humphrey U.S. Pat. No. 1,933,034 dated 5 Mar. 1935, or Littmann U.S. Pat. No. 1,933,035 dated 5 Mar. 1935, or Boggs U.S. Pat. No. 2,230,230 dated 4 Feb. 1941. Coreaction of the alpha-beta unsaturated carboxylic acids, e.g., maleic, with an unsaturated hydrocarbon polymer is shown in Rowland et al U.S. Pat. No. 2,608,550 dated 25 Aug. 1952. The coreaction products therein described may be neutralized to form salts, and used with other resinous materials. Copolymerization of a diolefin with a monoolefin, e.g., butadiene, myrcene, alloocimene, etc., with an octene such as diisobutylene followed by maleinization and neutralization is disclosed by Sparks in U.S. Pat. No. 2,634,256 dated 7 Apr. 1953. These productg may be water soluble in which case they are useful for treatment of paper, textiles, leather goods, sizing, etc.
Aldrich et al in U.S. Pat. No. 3,193,449 dated 6 July 1965 discloses terpene polymers reacted with maleic anhydride, neutralized, and emulsified to form a sizing composition for paper in place of rosin size. These materials are similar to the tackifier compositions useful in this invention.
Kincannon in U.S. Pat. No. 3,375,130 dated 26 Mar. 1968 discloses that the reaction product of maleic anhydride with polymerized terpenes (disclosed in U.S. Pat. No. 2,321,750) may be used in the bonding of molten polyolefin to a hydrophilic substrate such as cellulose or glass.
Weymann et al in U.S. Pat. No. 3,413,240 dated 26 Nov. 1968 have disclosed pressure sensitive adhesive compositions comprising a rubbery elastomer and a copolymer of a cyclic monoterpene hydrocarbon and styrene or substituted styrene. The rubber elastomer is first mixed with the tackifier and may then be emulsified or dispersed in water.
Erikson et al in U.S. Pat. No. 3,422,044 dated 14 Jan. 1969 discloses coating compositions using a maleinized drying oil, hydrolyzed, and neutralized for water dispersability. This reaction product can be combined with a latex to form a coating composition.
Wheeler in U.S. Pat. No. 3,478,005 dated 11 Nov. 1969 discloses terpene copolymers with a conjugated C.sub.5 diolefin feedstock. These copolymers are said to be tackifiers for pressure sensitive adhesives, e.g., a rubbery elastomer such as natural rubber or a synthetic rubber. The tackifiers are not maleinized.
Patzschke et al in U.S. Pat. No. 4,101,495 discloses modified olefin polymers containing carboxyl groups introduced as by maleinizing, neutralized with a base, and useful in coating compositions, e.g., electrodip-lacquering compositions.
British Pat. No. 978,292 published 23 Dec. 1964 discloses sizing agents made from petroleum resin (polymerized hydrocarbons), maleinized, mixed with tall oil or maleinized tall oil, saponified with alkali and dispersed homogeneously in water to improve the emulsifying property and adhesion to the paper pulp.
None of the prior art of which we are aware discloses an adhesive composition formed from an emulsified tackifier blended with a latex, and particularly natural rubber latex.
It is, therefore, a principal objective of the present invention to provide a novel adhesive composition composed of a tackifier formed from a resinous hydrocarbon polymer and elastomeric latex polymers in general, and natural rubber latices in particular.